Ventilation fans for venting hot air from attic areas underneath roofs have been increasing in popularity over the years. Hot air is known to accumulate under roof tops especially in attic areas. This buildup of hot air can lead to poor cooling conditions within the building and increased utility costs to run air conditioning systems and cooling systems, and the like. Thus, it is desirable to improve and maximize air removal rates from under roofs and from attic spaces, and the like.
Existing attic ventilation fans have been used but have substantial power requirements from existing building electrical supplies. For example, the GRAINGER® catalog sells an automatic power attic gable ventilator model number 4YN78 having metal type blades that rotate at 1050 RPM (revolutions per minute) generating 1320 cfm (cubic feet per minute) and requires 200 Watts of power. Another GRAINGER® attic fan model 4YN77 generates a higher level of cfm (1620 cfm) but requires 225 Watts of power.
Most existing attic ventilation fans use standard stamped generally flat metal fan blades that have only fair air moving performance. Flat type blades are not designed to maximize moving of air.
Various attic type ventilation fans have been proposed over the years. See for example, U.S. Pat. Nos. Des. 261,803 to Bohanon, Jr.; 4,501,194 to Brown; 5,078,047 to Wimberly; 6,306,030 to Wilson; and 6,695,692 to York. However, none of the cited references, individually or in combination overcome all the problems with the prior art described above.                The inventors and assignee of the subject invention have been at the forefront of inventing high efficiency ceiling fans by using novel twisted blade configurations. See for example, U.S. Pat. Nos. 6,884,034 and 6,659,721 and 6,039,541 to Parker et al. However, these fans are designed for maximizing air flow from ceiling fans that have much larger diameters (approximately 42 inches to 64 inches, etc.) and that operate at different speeds (less than approximately 200 RPM) than small diameter ventilation fans that are needed to exhaust air from underneath roofs and from attic spaces.        
Additionally, the inventors and assignee have worked on air conditioner condenser fan blades (see for example, U.S. Pat. Nos. D510,998 to Parker et al. and 7,014,423 to Parker et al. However, the air conditioner condenser fans are not optimized for the ventilation and removal of air from underneath roofs and from attic spaces. Aircraft, marine and automobile engine propeller type blades have been altered over the years to shapes other than flat rectangular. See for example, U.S. Pat. Nos. 1,903,823 to Lougheed; 1,942,688 to Davis; 2,283,956 to Smith; 2,345,047 to Houghton; 2,450,440 to Mills; 4,197,057 to Hayashi; 4,325,675 to Gallot et al.; 4,411,598 to Okada; 4,416,434 to Thibert; 4,730,985 to Rothman et al. 4,794,633 to Hickey; 4,844,698 to Gornstein; 5,114,313 to Vorus; and 5,253,979 to Fradenburgh et al.; Australian Patent 19,987 to Eather. However, these patents are generally used for high speed water, aircraft, and automobile applications where the propellers are run at high revolutions per minute (rpm) generally in excess of 500 rpm. None of these propellers are designed for optimizing airflow to remove undesirable air from attics and from underneath roofs.
Portable fans such as handheld battery fans have been used over the years. Similar to the problems presented above, small portable fans do not have blades aerodynamically optimized for airflow.
In addition, portable fans have batteries that have limited lifespans since the batteries either need to be constantly recharged from a 120 volt power supply or the batteries need to be constantly replaced.
The need for efficient powered portable fans has been growing much more in recent years. Natural disasters such as hurricanes and earthquakes have caused extensive power outages that can last from several hours to weeks or more in the United States. Conventional battery powered fans, cannot be used effectively during these disaster conditions. The prior art listed above does not fix the problems with portable fan use.
Thus, the need exists for better performing fans over the prior art.